A titanium alloy and a method for controlling its microstructure to improve its specific dynamic properties.

Abstract

This invention belongs to the field of wrought titanium alloy technology, and relates to a titanium alloy and a method for controlling its microstructure to improve its specific dynamic properties. The nominal composition of the titanium alloy consists of 5 to 7 alloying elements, namely: Al, Sn, Zr, and 2 to 4 of Mo, Cr, Nb, Fe, Ni, V, and Mn. A quantitative control method for the nominal composition based on molybdenum equivalent, aluminum equivalent, and density equivalent is proposed, and a microstructure control method for the titanium alloy based on this composition is proposed: 1. Ingot preparation; 2. Efficient ingot blanking; 3. Dual-phase spheroidizing forging of forged billets; 4. Final forming of billets; 5. Heat treatment of forgings. This method is simple, accurate, and efficient, leveraging the synergistic effect of composition and microstructure, and can balance the low density and high dynamic properties of the alloy, meeting the application requirements of equipment development for titanium alloys with high specific dynamic properties.

Description

Technical Field

[0001] This invention belongs to the field of wrought titanium alloy technology, and relates to a titanium alloy with high specific dynamic properties and a microstructure control method to improve its specific dynamic properties. Background Technology

[0002] Titanium alloys possess excellent properties such as low density, high strength, high toughness, fatigue resistance, corrosion resistance, and impact resistance, making them an important structural material widely used in aerospace, weaponry, and other fields. Most existing structural titanium alloys are developed based on performance requirements such as static strength, fatigue strength, damage tolerance, and thermal strength, meeting the application needs of aircraft, engines, spacecraft, and armored vehicles. Components requiring high penetration capability and high-speed impact resistance demand materials with lightweight and high dynamic properties, including four key indicators: density, maximum plastic strain, mean flow stress, and impact absorption energy. Lower density and higher maximum plastic strain, mean flow stress, and impact absorption energy result in greater component performance. Existing titanium alloys have shown significant potential to replace steel, improving specific dynamic properties and yielding certain benefits. Specific dynamic properties refer to the ratio of the dynamic properties (maximum plastic strain, mean flow stress, and impact absorption energy) of a titanium alloy to its density.

[0003] However, titanium alloys exhibit unique dynamic properties at high strain rates, and their response characteristics to composition, processing, and microstructure differ from conventional properties such as static strength, fatigue strength, and thermal strength. Due to the need for further improvement in specific dynamic properties, existing methods for controlling composition and microstructure are not entirely applicable, thus failing to fully tap the potential of titanium alloys, hindering their development, and failing to meet the application requirements of high-end manufacturing industries for titanium alloy components with high specific dynamic performance. Summary of the Invention

[0004] The purpose of this invention is to provide a titanium alloy with high specific dynamic properties and a method for controlling its microstructure to improve these properties.

[0005] To solve this technical problem, the technical solution of the present invention is as follows:

[0006] On the one hand, a titanium alloy is provided, wherein the nominal composition of the titanium alloy consists of 5 to 7 alloying elements, namely:

[0007] Two to four of the following: α-stable element Al, neutral elements Sn and Zr, and β-stable elements Mo, Cr, Nb, Fe, Ni, V, and Mn.

[0008] The nominal composition of the alloy is based on aluminum equivalent [Al]. eq. , Mo equivalent [Mo] eq. And density equivalent [ρ] eq. control:

[0009] According to formula [Al] eq. The aluminum equivalent [Al] is calculated as [Al] + 0.17[Zr] + 0.33[Sn]. eq. It ranges from 6.75% to 7.5%.

[0010] According to the formula [Mo] eq. =[Mo]+0.2[Ta]+0.28[Nb]+0.4[W]+0.67[V]+1.25[Cr]+1.25[Ni]+1.7[Mn]+1.7[Co]+2.5[Fe] Calculated Mo equivalent [Mo] eq. It ranges from 7.5% to 10.0%.

[0011] According to the formula [ρ] eq. =1 / ∑([E] / ρ E Calculated density equivalent [ρ] eq. ≤4.60g / cm 3 ,

[0012] Where E represents the alloying element in the alloy, [E] represents the mass percentage of the element, and ρ E This represents the density of the element E.

[0013] On the other hand, a method for controlling the microstructure to improve the specific dynamic properties of the titanium alloy is provided, the method comprising the following steps:

[0014] Step 1: Ingot Preparation: Prepare alloy ingots;

[0015] Step 2: Efficient Ingot Drafting

[0016] The alloy ingot obtained in step one is subjected to 4 to 8 upsetting and drawing deformations in the β single-phase region at 1100℃~1200℃. Each upsetting and drawing deformation is carried out in 1 to 3 rounds, with the upsetting and drawing deformation amounts being 20%~35% respectively. Hot material is returned to the furnace between the upsetting and drawing cycles, and the last upsetting cycle is cooled by oil or water.

[0017] Through multiple upsetting and drawing processes in the β single-phase region, the deformation is accumulated and combined with the heat treatment of the β single-phase region. The β phase is broken and homogenized as much as possible under sufficient thermomechanical action. Through the final rapid cooling treatment, the α phase precipitates in the smallest possible size under the synergistic effect of high distortion energy and high supersaturation. Finally, a forging blank with fine lamellar α phase structure distributed in a uniform fine-grained β phase matrix is ​​obtained, which lays the foundation for subsequent fine-grained spheroidization of α and β dual phases.

[0018] Step 3: Dual-phase spheroidizing reforging of the forged billet:

[0019] The forging billet obtained in step two is subjected to upsetting and drawing deformation at 60℃~150℃ below the β transformation temperature for 4~8 times. Each time upsetting and drawing deformation is alternated for 1~2 rounds, and the upsetting and drawing deformation amounts are 30%~50%. The first 1~3 times are controlled by four-sided reversing drawing, and the remaining times are controlled by hexagonal drawing followed by rounding, thus completing the control of the forging billet deformation structure.

[0020] In terms of deformation, upsetting and four-way reversible elongation make the deformation of the forging billet more uniform in all directions, which improves the uniformity of the forging billet's structure macroscopically and is more conducive to the rapid spheroidization of the α phase microscopically. Combined with the high-uniformity hexagonal elongation and rounding deformation in the final stage, the high-uniformity and high-spheroidization effect of the forging billet structure is achieved through modified forging. In terms of structure evolution control, based on the fine-grained β and fine-lamellar α phase structure, the number and proportion of α phases participating in deformation are increased through deformation modified forging at a lower temperature, which increases the content and proportion of spheroidized α phase in the structure of the modified forging billet, and finally obtains a high-α phase two-phase spheroidized billet, providing a structural basis for high dynamic performance control.

[0021] Step 4: Final shaping of the billet:

[0022] The billet obtained in step three is formed at the same temperature as in step three to obtain a forging;

[0023] Step 5: Heat treatment of forgings:

[0024] The forgings obtained in step four are subjected to heat treatment at a temperature 20°C to 50°C lower than that in step three, and held at that temperature for 1 hour to 3 hours.

[0025] Step five eliminates distortion energy, making the microstructure more uniform and stable, and weakening or even eliminating anisotropy. On the other hand, it makes full use of the microstructure evolution law during the cooling process of the dual-phase spheroidized titanium alloy, increasing the content of spheroidized α phase while avoiding the reduction of the number of α phase, thereby obtaining a microstructure with high dynamic performance.

[0026] In step one, an alloy ingot is prepared using a multi-stage vacuum consumable melting process.

[0027] Preferably, the elongation deformation in step two is controlled by hexagonal elongation followed by rounding.

[0028] Preferably, hot material is recycled between the three firing cycles in step three.

[0029] The specific dynamic properties of the titanium alloy refer to the ratio of the dynamic properties of the titanium alloy to its density; the dynamic properties include maximum plastic strain, average rheological stress, and impact absorption energy.

[0030] Through the above-described microstructural control methods, the maximum specific plastic strain of the titanium alloy exceeds 0.056 cm. 3 / g, with a specific average rheological stress exceeding 338 MPa / (g / cm²). 3 The specific impact absorption energy is greater than or equal to 90 (J / cm). 3 ) / (g / cm 3 ).

[0031] The beneficial effects of this invention are:

[0032] This invention proposes a quantitative control method for nominal composition based on molybdenum equivalent, aluminum equivalent, and density equivalent. This method is simple, accurate, and reliable. Using Al, Sn, and Zr as the main alloying elements, supplemented by 2-4 low-density β-stabilizing elements, it simultaneously increases the aluminum and molybdenum equivalents, balancing the alloy's low density and high dynamic performance, laying the foundation for improving the alloy's specific dynamic properties. Simultaneously, based on this titanium alloy composition, a highly efficient and high-yield microstructure control method is proposed. This involves efficient billet preparation of ingots obtained from consumable metallurgy through multiple upsetting and drawing processes in the β single-phase region. This allows the β phase to undergo sufficient thermomechanical treatment to achieve thorough homogenization and refinement. Rapid cooling further refines the α-lamellae. Based on this, a deformation control method using reversing upsetting and hexagonal elongation at lower temperatures in the two-phase region is employed to achieve a uniform macrostructure in the forged billet and obtain a high-α-phase-content two-phase spheroidized microstructure. Heat treatment achieves a final microstructure that is uniform, stable, fine, and spheroidized, giving the alloy high dynamic performance. The method disclosed in this invention can be performed using general-purpose equipment. The combined effect of composition and microstructure control methods has improved the matching between alloy density and high dynamic performance. Attached Figure Description

[0033] Figure 1 This is a diagram of the uniform fine-grained β macrostructure obtained after efficient billet preparation of the ingot;

[0034] Figure 2 This is a diagram showing the microstructure of fine lamellar α phase distributed in a uniform fine-grained β phase matrix obtained after efficient billet preparation in ingot casting;

[0035] Figure 3 This is a diagram of the high-α-content duplex spheroidized microstructure obtained after duplex spheroidizing reforging.

[0036] Figure 4 This is a diagram of the high α-content biphase spheroidized microstructure obtained after heat treatment. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The features of various aspects of the embodiments of the present invention will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can also be practiced without these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples. The invention is not limited to any specific setups and methods provided below, but covers all improvements, substitutions, etc., to product structures and methods without departing from the spirit of the invention.

[0039] In the various accompanying drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the invention.

[0040] Table 1 below shows the nominal composition of the high-specific-dynamic-performance titanium alloys according to the present invention, in aluminum equivalent [Al]. eq. , Mo equivalent [Mo] eq. And density equivalent [ρ] eq. Table of component content of the controlled embodiments.

[0041] Table 1 Nominal composition of high specific dynamic performance titanium alloys

[0042]

[0043] The steps for controlling the microstructure of high-specific-performance titanium alloys in Table 1 are as follows:

[0044] Step 1: Ingot preparation: Alloy ingots are prepared using a multi-stage vacuum arc remelting process;

[0045] Step 2, Efficient Ingot Drafting: The alloy ingot obtained in Step 1 is subjected to 4 to 8 upsetting and drawing deformations at 1100℃~1200℃. Each upsetting and drawing deformation is alternated for 1 to 3 rounds, with the upsetting and drawing deformation amounts being 20%~35% respectively. Hot material is recycled between the firings, and the last firing is oil-cooled or water-cooled to obtain a uniform fine-grained forging billet.

[0046] Step 3: Dual-phase spheroidizing forging of billet: The forging billet obtained in Step 2 is subjected to upsetting and drawing deformation at 60℃~150℃ below the β transformation temperature for 4~8 times. Each time, upsetting and drawing deformation are alternated for 1~2 rounds, and the upsetting and drawing deformation amounts are 30%~50%. Among them, the first 1~3 times are controlled by four-sided reversing drawing, and the remaining times are controlled by hexagonal drawing followed by rounding. This completes the control of the forging billet deformation structure and obtains a dual-phase spheroidized billet.

[0047] Step 4: Final forming of the billet: The billet obtained in Step 3 is formed at the same temperature as in Step 3 to obtain the forging;

[0048] Step 5: Heat treatment of forgings: The forgings obtained in Step 4 are heat treated at a temperature 20℃ to 50℃ lower than that in Step 3, and held for 1 to 3 hours to obtain a microstructure with high dynamic performance.

[0049] The specific steps and processes for controlling the microstructure and dynamic properties of the titanium alloy described in Example 9 of Table 1 are as follows:

[0050] Step 1: Ingot preparation: Alloy ingots are prepared using a three-stage vacuum arc remelting process;

[0051] Step 2, Efficient Ingot Drafting: The alloy ingots obtained in Step 1 are subjected to upsetting and drawing deformation at 1150℃ and 1100℃ for 2 rounds each. Each round of upsetting and drawing deformation is completed in 2 cycles, with the upsetting and drawing deformation amount being 25% each. The drawing adopts a hexagonal drawing and then rounding deformation method. Hot material is recycled between rounds, and water cooling is used in the last round to obtain a uniform fine-grained forging billet.

[0052] Step 3: Dual-phase spheroidizing forging of the forging billet: The forging billet obtained in Step 2 is subjected to a process at 830℃ (T β =905℃) First, perform 3 upsetting and four-sided reversing elongation deformation, with each upsetting and elongation deformation alternating for 1 round. Then, perform 2 upsetting and hexagonal rolling elongation deformation, with each upsetting and elongation deformation alternating for 1 round. The upsetting and elongation deformation amounts are both 40%, thus completing the control of the forging billet deformation structure and obtaining a two-phase spheroidized billet.

[0053] Step 4: Final forming of the billet: The billet obtained in Step 3 is extruded at 830℃ to obtain a forging;

[0054] Step 5: Heat treatment of forgings: Hold the forgings obtained in step 4 at 800℃ for 3 hours to obtain a high dynamic performance microstructure.

[0055] The dynamic performance results of the titanium alloy obtained using the components in Table 1 and the microstructure control method of the present invention are shown in Table 2.

[0056] Table 2 Performance of high specific dynamic properties titanium alloys

[0057]

[0058] In Table 2, the specific maximum plastic strain refers to the ratio of the corresponding alloy's maximum plastic strain to its density; the specific average flow stress refers to the ratio of the corresponding alloy's average flow stress to its density; and the specific impact absorption energy refers to the ratio of the corresponding alloy's impact absorption energy to its density. As can be seen from Table 2, the titanium alloy provided by this invention possesses high specific dynamic properties, with a specific maximum plastic strain (ε... up / ρ) exceeds 0.056cm 3 / g, up to a maximum of 0.061cm 3 / g; Specific average rheological stress (σ) a / ρ) exceeds 338MPa / (g / cm) 3 The maximum pressure reached 353 MPa / (g / cm). 3 ); specific shock absorption energy (E) AI / ρ) exceeds 90 (J / cm) 3 ) / (g / cm 3 The maximum value reached 97 (J / cm). 3 ) / (g / cm 3 The specific maximum plastic strain, specific average rheological stress, and specific impact absorption energy of existing titanium alloys are 0.048 cm⁻¹. 3 / g~0.054cm 3 / g、326MPa / (g / cm 3 )~327MPa / (g / cm 3 ), 79 (J / cm) 3 ) / (g / cm 3 )~83 (J / cm 3 ) / (g / cm 3 All three dynamic performance indicators showed significant improvement.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A titanium alloy, characterized in that: The nominal composition of the titanium alloy consists of 5 to 7 alloying elements, namely: Two to four of the following: α-stable element Al, neutral elements Sn and Zr, and β-stable elements Mo, Cr, Nb, Fe, Ni, V, and Mn. The nominal composition of the alloy is based on aluminum equivalent [Al]. eq. , Mo equivalent [Mo] eq. And density equivalent [ρ] eq. control: According to formula [Al] eq. The aluminum equivalent [Al] is calculated as [Al] + 0.17[Zr] + 0.33[Sn]. eq. It ranges from 6.75% to 7.5%. According to the formula [Mo] eq. =[Mo]+0.2[Ta]+0.28[Nb]+0.4[W]+0.67[V]+1.25[Cr]+1.25[Ni]+1.7[Mn]+ 1.7[Co]+2.5[Fe] Calculated Mo equivalent [Mo] eq. The percentage is 7.5% to 10.0%. According to the formula [ρ] eq. =1 / Ʃ([E] / ρ E ) Calculated density equivalent [ρ] eq. ≤4.60g / cm 3 , Where E represents the alloying element in the alloy, [E] represents the mass percentage of the element, and ρ E The density of element E in its pure form; Titanium alloys possess high specific dynamic properties; the specific dynamic properties of titanium alloys refer to the ratio of their dynamic properties to their density; the dynamic properties include maximum plastic strain, average rheological stress, and impact absorption energy. The titanium alloy exhibits a maximum specific plastic strain exceeding 0.056 cm. 3 / g, with a specific average rheological stress exceeding 338 MPa / (g / cm²). 3 The specific impact absorption energy is greater than or equal to 90 (J / cm). 3 ) / (g / cm 3 ).

2. A method for controlling the microstructure to improve the specific dynamic properties of the titanium alloy according to claim 1, characterized in that: The method steps are as follows: Step 1: Ingot Preparation: Prepare alloy ingots; Step 2: The alloy ingot obtained in Step 1 is subjected to 4 to 8 upsetting and drawing deformations in the β single-phase region at 1100℃~1200℃. Each upsetting and drawing deformation is carried out in 1 to 3 rounds, with the upsetting and drawing deformation amounts being 20%~35% respectively. Hot material is returned to the furnace between the upsetting and drawing cycles, and the last upsetting cycle is cooled by oil or water. Step 3, Dual-phase spheroidizing forging of billet: The billet obtained in Step 2 is subjected to upsetting and drawing deformation at 60℃~150℃ below the β transformation temperature for 4~8 times. Each time, upsetting and drawing deformation are alternated for 1~2 rounds, and the upsetting and drawing deformation amounts are 30%~50%. Among them, the first 1~3 times are controlled by four-sided reversing drawing, and the remaining times are controlled by hexagonal drawing followed by rounding, thus completing the control of the forging deformation structure. Step 4: Final forming of the billet: The billet obtained in Step 3 is formed at the same temperature as in Step 3 to obtain the forging; Step 5: Heat treatment of forgings: The forgings obtained in Step 4 are heat-treated at a temperature 20℃ to 50℃ lower than that in Step 3 for 1 to 3 hours.

3. The method according to claim 2, characterized in that: The elongation deformation in step two is controlled by hexagonal elongation followed by rounding.

4. The method according to claim 2, characterized in that: In step three, hot materials are returned to the furnace during the secondary firing process.

5. The method according to claim 2, characterized in that: In step one, an alloy ingot is prepared using a multi-stage vacuum consumable melting process.

6. The method according to claim 2, characterized in that: The forming method in step four is extrusion forming.

Images